This invention relates to the field of labels, particularly labels for diagnostic use. In particular, it relates to oligonucleotides that are modified to enhance the binding affinity of the oligonucleotides for complementary sequences and that in addition bear a readily detectable characteristic.
Sequence specific binding of oligonucleotides both to single stranded RNA and DNA and to duplex DNA is widely known. This phenomenon has been harnessed for a great variety of diagnostic, preparative and therapeutic purposes. Previously, one objective of research in this field has been to increase the affinity of such oligonucleotides for their complementary sequences. For example, Froehler et al. have described oligonucleotides containing 5-substituted pyrimidine bases that substantially increase the Tm for oligonucleotide binding to complementary bases (International Publication No. 92/10115).
Fluorescent cytosine derivatives are known for use in preparing labeled DNA probes. See Inoue et al., Jpn Kokai JP 62059293, (1987). In addition, fluorescent labeled nucleotides have been employed in DNA sequencing. See Prober et al., “Science” 238:336-341 (1987).
1,3-Dihydro-2H-imidazo[4,5-b]-quinolin-2-one derivatives as phosphodiesterase inhibitors are disclosed by Raeymaekers et al. (EP 541,153).